In the field of use of a print or type band for printing machines, such type band is normally installed in an endless loop on the printing machine. When the print band has been etched or formed with type characters, the ends of the band must be welded together to provide a continuous band for use on the printer. It is necessary of course that the ends of the band be perfectly aligned with each other to insure that the portions of the band on either side of the weld joint are parallel and that the ends of the band are square during welding to assure that the continuous band forms a true geometric cylinder like loop. Additionally, when the band is received for welding, the band generally has been formed in a preset condition and assumes a permanent set condition which is a curvature retained from the carrying of the print band on a spool during delivery thereof after the characters have been etched onto the band. It is therefore important that the welding fixture be of a nature to hold the ends of the print band in precise position and to maintain the alignment of the band during welding.
Representative prior art in welding apparatus includes U.S. Pat. No. 1,931,255, issued to A. J. Frantz on Oct. 17, 1933, which shows welding machine control of butt welding machines to provide control mechanism arranged to enable proper actuation and control of the welding machine from a single station. Use is made of compressed air, of electricity and of oil for control and clamping of the members to be welded.
U.S. Pat. No. 2,293,481, issued to L. A. Wilkie on Aug. 18, 1942, shows a welding device for welding band saws in the form of an endless band and includes means for automatically opening the welding circuit when the welding operation is completed.
U.S. Pat. No. 3,487,188, issued to W. J. Draving on Dec. 30, 1969, shows a method for butt welding the ends of a length of wire formed in a loop. The loop is positioned intermediate the wire holders for electrically shunting the discharge of a capacitive discharge type welding apparatus.
U.S. Pat. No. 3,768,148 issued to G. Pagnotta et al., on Oct. 30, 1973, discloses a method of joining print character bars to high speed printer fingers which includes forming spacer projections in the bar or finger blank prior to welding the parts together in order to provide a fixed gap between the finger and the bar for a uniform layer of weld material with a resulting uniform joint between the parts.